The present invention relates to a device for opening blocked tubes. More particularly the present invention relates to a device for opening blocked tubes in the human or animal body, particularly blocked blood vessels. For ease of reference, various tubes that may be found in the human or animal body will be referred to as "biological tubes".
Tubes may become blocked for a variety of reasons and the consequences of the blockages vary depending on the nature of the tube and the location of the blockage. Even partial blocking of tubes may cause difficulties such as reducing the rate of flow of any fluid flowing in the tube. Where the tube is a biological tube, partial blocking may result in the patient suffering from mild to severe pain depending on the extent of the blockage. The problem may be particularly severe where the partial blockage occurs in an artery such as a coronary artery.
Present techniques enable such partially blocked tubes to be opened by means of a technique known as hydraulic stretch. This technique, which is particularly common in the field of biological tubes and more particularly blood vessels requires that a guide wire is inserted into the vessel such that it extends through the narrowed region of the tube. A deflated balloon, located at the distal end of a catheter, is then passed along the guide wire to the narrowed segment. This may be via an over-the-wire technique where the catheter actually surrounds the wire or via an arrangement known as the mono-rail technique whereby the catheter is suspended from the wire.
Once the balloon is in place in the narrowing it is inflated and the narrowed artery is thereby stretched such that the pathway in the centre of the tube is fully opened. This technique is very effective and, in the case of biological tubes, as it is minimally invasive, often being performed under local anaesthetic through a percutaneous puncture from a remote site, is of minimal distress to the patient.
The same technique may be utilised where the occlusion is total, ie where the tube is substantially completely blocked, provided that the material forming the occlusion is sufficiently soft to enable the guide wire and the catheter to be pushed through the blocking mass.
However, if the occlusion is hard such as where it has been formed for some time, it may not be possible to push a guide wire through the blocking mass and thus a balloon catheter of the type described above cannot be used. It is therefore necessary for an alternative arrangement to be made for overcoming the effects of the blockage. Where the tube is a biological tube the patient generally will have to undergo major surgery such that the occlusion may be bypassed. Such operations are traumatic for the patient and it is therefore desirable that means be provided that enable total occlusions to be opened without the need for surgery, ie. that can be carried out with minimal trauma to the patient, such as through a percutaneous puncture under local anaesthetic.